The present invention relates to a system for indicating the pressure in an aircraft landing gear shock absorber, a kit for the same and a method of determining the pressure in an aircraft landing gear shock absorber, such as shock absorbers in a nose wheel oleo or in the main landing gear. The system, method and kits are particularly effective for larger aircraft.
It is desirable for the pressure in aircraft landing gear shock absorbers to be within certain limits. If the pressure within a landing gear shock absorber is too low, the shock absorber may “bottom out” during landing, for example, possibly causing damage to the landing gear. If the pressure within a landing gear shock absorber is too high, the ability of the shock absorber to dampen peak loading may be reduced. Furthermore, the shock absorber may rupture under the application of a large load (as may be applied if the aircraft is heavily laden and/or on a hard landing). Many landing gear shock absorbers are not fitted with pressure sensors. If pressure sensors are fitted to a landing gear shock absorber, then the pressure sensors are sometimes located in positions which may be difficult to access, for example, close to the fuselage or at the very bottom of the landing gear. As a secondary check to determine pressure, the ground crew typically measure the distance between two parts of the shock absorber. This distance, coupled with knowledge of the aircraft's weight and the ambient temperature, may be used to provide an estimate of the pressure in the shock absorber. This measurement is sometimes known by those skilled in the art as “the H measurement” because it involves measuring the height of one part of the shock absorber in relation to another part. This measurement is prone to significant error, not least because it is difficult to measure the distance between the two parts of the shock absorber with any accuracy. Furthermore, information relating the distance measured to the pressure in the shock absorber is contained on placards which are attached to the landing gear. These placards are often difficult to read, which may make it difficult to determine the pressure from the distance measurement taken. U.S. Pat. No. 6,128,951 discloses the measurement of pressure in landing gear shock absorbers using pressure sensors. U.S. Pat. No. 6,128,951 also discloses the use of a radial variable digital transducer to measure landing gear shock absorber compression and extension.
It is an aim of the present invention to ameliorate one or more of the problems mentioned above.